Loong Campion K P, Takeda Aya K, Badr Myriam A, Rogers Jordan S, Chase P Bryant
Department of Biological Science, The Florida State University, Tallahassee, FL, 32306, USA ; Department of Physics, The Florida State University, Tallahassee, FL, 32306, USA.
Cell Mol Bioeng. 2013 Jun 1;6(2):183-198. doi: 10.1007/s12195-013-0269-8.
Actomyosin kinetics in both skinned skeletal muscle fibers at maximum Ca-activation and unregulated motility assays are modulated by solvent microviscosity in a manner consistent with a diffusion limited process. Viscosity might also influence cardiac thin filament Ca-regulatory protein dynamics. motility assays were conducted using thin filaments reconstituted with recombinant human cardiac troponin and tropomyosin; solvent microviscosity was varied by addition of sucrose or glucose. At saturating Ca, filament sliding speed () was inversely proportional to viscosity. Ca-sensitivity ( ) of decreased markedly with elevated viscosity ( ≥ ~1.3). For comparison with unloaded motility assays, steady-state isometric force () and kinetics of isometric tension redevelopment ( ) were measured in single, permeabilized porcine cardiomyocytes when viscosity surrounding the myofilaments was altered. Maximum Ca-activated changed little for sucrose ≤ 0.3 M ( ~1.4) or glucose ≤ 0.875 M ( ~1.66), but decreased at higher concentrations. Sucrose (0.3 M) or glucose (0.875 M) decreased for . at saturating Ca decreased steeply and monotonically with increased viscosity but there was little effect on at sub-maximum Ca. Modeling indicates that increased solutes affect dynamics of cardiac muscle Ca-regulatory proteins to a much greater extent than actomyosin cross-bridge cycling.
在最大钙激活状态下的皮肤化骨骼肌纤维和无调节的运动分析中，肌动球蛋白动力学受溶剂微粘度的调节，其方式与扩散受限过程一致。粘度也可能影响心脏细肌丝钙调节蛋白的动力学。使用重组人心肌肌钙蛋白和原肌球蛋白重构的细肌丝进行运动分析；通过添加蔗糖或葡萄糖来改变溶剂微粘度。在饱和钙状态下，细肌丝滑动速度（）与粘度成反比。随着粘度升高（≥1.3），的钙敏感性（）显著降低。为了与无负荷运动分析进行比较，当肌丝周围的粘度改变时，在单个透化猪心肌细胞中测量稳态等长力（）和等长张力重建动力学（）。对于蔗糖≤0.3 M（1.4）或葡萄糖≤0.875 M（~1.66），最大钙激活的变化不大，但在较高浓度下会降低。蔗糖（0.3 M）或葡萄糖（0.875 M）会降低的。在饱和钙状态下，随着粘度增加急剧且单调下降，但在次最大钙状态下对影响不大。模型表明，溶质增加对心肌钙调节蛋白动力学的影响比对肌动球蛋白横桥循环的影响大得多。
